issues with sites in a network

I’m trying to set-up a multisite for testing functionalities and learning about it, first time I attempt this.

I have intalled WP, activated multisite, and created two “sub-sites” with admins.

Problems I have:

1) sub-sites are shown without theme/css
2) I cannot log-in with sub-sites admins

Test website is here: https://www.dedalusuk.com/
Sites in the network are linked in the widgets on the right: “Centro Studi Sociali” and “Domus Cultura”

Any help would be appreciated